The present invention relates to a direct current motor and particularly to a direct current motor improved with respect to commutating characteristics, provided with a field magnet having 2np magnetic poles (n being an integer of 1 or more and p being an interger of 2 or more) and a disc-shaped or cylindrical armature comprising n (py.+-.1) armature coils (y being an integer of 3 or more but 4 or more when p=2), with the lapping of the armature coils minimized.
It is well known that a direct current (DC) motor, provided with a plurality of armature coils formed in a lap-winding manner or a wave-winding manner is highly efficient and has better commutating characteristics as the number of armature coils increases. However, if the conventional manner of lap winding or wave winding is employed in a coreless motor, the armature will increase in thickness because the armature coils are superimposed on each other in many layers. The increased thickness of the armature will substantially reduce the effective magnetic field of the field magnet which passes through the armature, resulting in decreased magnetic field, motor efficiency and starting torque. In order to solve these problems, the prior art effort has been directed to decreasing the thickness of the electrically conductive portions contributing to the generation of torque. The process for decreasing the thickness of the electrically conductive portions is performed by press molding, and accordingly is often accompanied by such defects as breaking and short-circuiting of the armature coils. Further, since the phase relationship between the armature cannot be positively held in the desired state at the time the coils are arranged, correct phase relationship between the armature coils is liable to be distorted. Accordingly, such prior art DC motors are costly and cannot be mass produced.
Another prior art technique used for conventional cylindrical coreless DC motors, for avoiding superimposition of the opposite edge portions of the armature coils on each other, requires that the insulated wire be wound in alignment, so that a cylindrical armature is formed, with the entire width of winding, or a part thereof slanting with respect to the rotating axis. This technique however, also is costly and cannot be used for mass-production.